There is a conventional technique of reducing a target voltage based on information on the operation of a throttle, for example, in order to reduce the load on the engine of a motorcycle during acceleration (see J270445B, for example). As the target voltage decreases, the amount of the electric power generated by a motor (generator) connected to the engine (i.e., the amount of the electricity with which a battery is charged) decreases, and therefore, the load on the engine decreases. Thus, the acceleration performance of the engine can be prevented from deteriorating.
For example, a user operates the throttle to accelerate the engine. According to the conventional technique described above, the time for the engine to accelerate is recognized based on the amount of the movement of the throttle caused by the operation, and the target voltage is changed according to the recognized time.
According to the conventional technique described above, the time to accelerate is recognized based on the amount of the movement of the throttle. Therefore, there is a problem that an additional sensor that detects the amount of the movement of the throttle is needed, and therefore the manufacturing cost of the motorcycle increases.